1. Field of Invention
Embodiments of the invention relate to a routing mechanism in communication networks such as the Internet. More specifically, embodiments of the invention relate to mechanisms and methods for constructing Autonomous System (AS) disjoint Traffic Engineering Label Switched Path (TE-LSP) over a computer or telecommunications network.
2. Description of the Background Art
With increased network traffic, Internet service providers (ISPs) have increasingly turned to Traffic Engineering Label Switched Path (TE-LSP) to overcome bandwidth constraints and direct network traffic to under utilized paths. Traffic engineering also provides the ISP a mechanism to analyze current traffic loads and direct traffic flow onto paths that would otherwise remain underutilized.
With TE-LSP, an ISP is able to map traffic onto the existing physical topology and to move traffic flow away from the shortest, lowest cost metrics, path to under-utilized paths. This allows the ISP to better utilize their entire network capacity.
Current mechanisms for building inter-domain TE-LSPs involve constructing separate sections of a path through each AS using Interior Gateway Protocol (IGP) or Interior Border Gateway Protocol (iBGP). After the traffic traverses an AS, it is handed off to the next AS which constructs, in turn, a path through the AS to the next intermediate AS and so on until a path, spanning multiple ASs, is constructed from the source to the destination while avoiding network bottlenecks.
While TE-LSP provides the ISP a mechanism to achieve effective utilization of network resources within the domain, a bottleneck may develop in another intermediate ASs that can delay the traffic. To avoid that problem, it is necessary to construct multiple dis-joint paths from the source to the destination. However, the PCE constructs only a single TE-LSP so the risk of a problem in one domain affecting timely delivery of the traffic is still quite high. Further, current TE-LSP are not flexible enough to construct AS-disjoint TE-LSPs to act as a backup TE-LSP that traverses none of the intermediate ASs traversed by the primary TE-LSP.
What is needed is a mechanism that enables ISPs to construct multiple AS-disjoint TE-LSPs to better control network traffic flow, to load balance traffic along various paths through each domain and to provide reliable backup transport should an AS on the single TE-LSP experience a disruption. There is also a need for a mechanism that can construct AS disjoint paths such that the head-end AS can define two TE-LSPs that traverse different intermediate ASs to reach a common destination. More specifically, what is needed is the ability to construct both a primary TE-LSP and a backup TE-LSP that traverses none of the intermediate ASs that the primary TE-LSP traverses. What is still further needed is a mechanism that enables ISPs to construct a partially disjoint backup TE-LSP when dictated by engineering considerations. What is still further needed is a mechanism that can load balance traffic across multiple TE-LSPs that are either fully or partially disjoint.